Method and apparatus for performing robust cadence detection in a video deinterlacer

1. A deinterlacing apparatus, comprising:

a buffer to receive a plurality of consecutive fields of an interlaced video;

a field combination module, coupled to the buffer, to deinterlace the interlaced video in accordance with cadence of the interlaced video; and

a cadence detection module to detect the cadence by

(1) causing each of the fields to be combined with its preceding field into a frame and with its subsequent field into another frame to obtain a plurality of combined frames,

(2) determining a comb factor of each of the combined frames to obtain a sequence of comb factors of the combined frames by determining a comb factor value of each pixel in the frame and accumulating the comb factor value over all of the pixels within the frame to obtain the comb factor of that frame, and declaring the comb factor of a combined frame to be a high value if the accumulated comb factor value over all the pixels within the combined frame exceeds a pre-determined threshold while declaring the comb factor of the combined frame to be a low value if the accumulated comb factor value does not exceed the pre-determined threshold, and

(3) determining if the sequence of comb factors of the combined frames follows a pre-determined repeating pattern.

2. The apparatus of claim 1 , wherein the cadence detection module detects a 2:2 cadence if the sequence of comb factors is detected to follow a low-high-low-high repeating pattern for a pre-determined number of times.

3. The apparatus of claim 1 , wherein the cadence detection module causes the field combination module to produce the combined frames.

4. A method of detecting cadence of an interlaced video, comprising:

receiving a plurality of consecutive fields of the interlaced video;

while receiving the fields, combining the fields into a plurality of combined frames such that each of the fields is combined with its preceding field into a frame and with its subsequent field into another frame to ensure that each of the fields is included in two adjacent combined frames;

determining a comb factor of each of the combined frames to obtain a sequence of comb factors of the combined frames, wherein the determining a comb factor of each of the combined frames further comprises

determining a comb factor value of each pixel in the frame;

accumulating the comb factor value over all of the pixels within the frame to obtain the comb factor of the frame;

declaring the value of the comb factor of the frame to be high if the accumulated comb factor value over all the pixels within the frame exceeds a pre-determined threshold; and

declaring the value of the comb factor of the frame to be low if the accumulated comb factor value over all the pixels within the frame does not exceed the pre-determined threshold;

determining if the sequence of comb factors of the combined frames follows a pre-determined repeating pattern;

declaring detection of the cadence if the sequence of comb factors of the combined frames is detected to follow the pre-determined repeating pattern; and

deinterlacing the interlaced video in accordance with the detected cadence using field combination.

5. The method of claim 4 , wherein the pre-determined repeating pattern is a high-low-high-low pattern repeated for a predetermined number of times.

6. The method of claim 5 , wherein the cadence detected is 2:2 cadence.

7. The method of claim 4 , wherein the determining a comb factor value of each pixel in the frame further comprises

interpolating a pixel vertically with a pixel above and a pixel below to generate an interpolated pixel for the pixel;

determining whether the value of the pixel falls outside a pre-determined range of the interpolated pixel;

declaring the value of the comb factor of the pixel to be high if the value of the pixel falls outside the pre-determined range of the interpolated pixel; and

declaring the value of the comb factor of the frame to be low if the value of the pixel falls inside the pre-determined range of the interpolated pixel.

8. The method of claim 4 , further comprising invoking field extension deinterlacing by interpolation if cadence is not detected for the interlaced video.

9. A non-transitory computer-readable recording medium having sequences of instructions, the sequences of instructions including instructions which, when executed, cause a processor to perform cadence detection of an interlaced video, further comprising:

receiving a plurality of consecutive fields of the interlaced video;

while receiving the fields, combining the fields into a plurality of combined frames such that each of the fields is combined with its preceding field into a frame and with its subsequent field into another frame to ensure that each of the fields is included in two adjacent combined frames;

determining a comb factor of each of the combined frames to obtain a sequence of comb factors of the combined frames, wherein the determining a comb factor of each of the combined frames further comprises

determining a comb factor value of each pixel in the frame;

accumulating the comb factor value over all of the pixels within the frame to obtain the comb factor of the frame;

declaring the value of the comb factor of the frame to be high if the accumulated comb factor value over all the pixels within the frame exceeds a pre-determined threshold; and

declaring the value of the comb factor of the frame to be low if the accumulated comb factor value over all the pixels within the frame does not exceed the pre-determined threshold;

determining if the sequence of comb factors of the combined frames follows a pre-determined repeating pattern;

declaring detection of the cadence if the sequence of comb factors of the combined frames is detected to follow the pre-determined repeating pattern; and

deinterlacing the interlaced video in accordance with the detected cadence.

10. The non-transitory computer-readable recording medium of claim 9 , wherein the pre-determined repeating pattern is a high-low-high-low pattern repeated for a predetermined number of times.

11. The non-transitory computer-readable recording medium of claim 9 , wherein the cadence detected is 2:2 cadence.

12. The apparatus of claim 1 , wherein the cadence detection module declares that no cadence is detected if the sequence of comb factors does not follow a low-high-low-high repeating pattern for a pre-determined number of times.

13. The apparatus of claim 12 , wherein if the cadence detection module does not detect the cadence of the interlaced video, the cadence detection module invokes a field extension deinterlacing module to deinterlace the interlaced video.

14. A deinterlacing apparatus, comprising:

means for receiving a plurality of consecutive fields of an interlaced video;

means for deinterlacing the interlaced video in accordance with cadence of the interlaced video; and

means for detecting the cadence by

(1) causing each of the fields to be combined with its preceding field into a frame and with its subsequent field into another frame to obtain a plurality of combined frames,

(2) determining a comb factor of each of the combined frames to obtain a sequence of comb factors of the combined frames by determining a comb factor value of each pixel in the frame and accumulating the comb factor value over all of the pixels within the frame to obtain the comb factor of that frame, and declaring the comb factor of a combined frame to be a high value if the accumulated comb factor value over all the pixels within the combined frame exceeds a pre-determined threshold while declaring the comb factor of the combined frame to be a low value if the accumulated comb factor value does not exceed the pre-determined threshold, and

(3) determining if the sequence of comb factors of the combined frames follows a pre-determined repeating pattern.

15. The apparatus of claim 14 , wherein the means for detecting the cadence detects a 2:2 cadence if the sequence of comb factors is detected to follow a low-high-low-high repeating pattern for a pre-determined number of times.

16. The method of claim 4 , further comprising declaring that no cadence is detected if the sequence of comb factors does not follow a low-high-low-high repeating pattern for a pre-determined number of times.

17. The non-transitory computer-readable recording medium of claim 9 , further comprising

declaring that no cadence is detected if the sequence of comb factors does not follow a low-high-low-high repeating pattern for a pre-determined number of times; and

invoking field extension deinterlacing by interpolation if cadence is not detected for the interlaced video.

18. The non-transitory computer-readable recording medium of claim 9 , wherein the determining a comb factor value of each pixel in the frame further comprises

interpolating a pixel vertically with a pixel above and a pixel below to generate an interpolated pixel for the pixel;

determining whether the value of the pixel falls outside a pre-determined range of the interpolated pixel;

declaring the value of the comb factor of the pixel to be high if the value of the pixel falls outside the pre-determined range of the interpolated pixel; and

declaring the value of the comb factor of the frame to be low if the value of the pixel falls inside the pre-determined range of the interpolated pixel.

19. The interlacing apparatus of claim 14 , wherein the cadence detected is 2:2 cadence.

20. The interlacing apparatus of claim 14 , wherein if the means for detecting cadence does not detect the cadence of the interlaced video, the means for detecting cadence invokes a field extension deinterlacing means to deinterlace the interlaced video.

21. The interlacing apparatus of claim 14 , wherein the means for detecting the cadence further comprises

means for interpolating a pixel vertically with a pixel above and a pixel below to generate an interpolated pixel for the pixel;

means for determining whether the value of the pixel falls outside a pre-determined range of the interpolated pixel;

means for declaring the value of the comb factor of the pixel to be high if the value of the pixel falls outside the pre-determined range of the interpolated pixel; and

means for declaring the value of the comb factor of the frame to be low if the value of the pixel falls inside the pre-determined range of the interpolated pixel.